This invention relates to an infinite speed ratio transmission device which can hold an output rotation relative to an input rotation to zero by combining a continuously variable transmission, a fixed speed ratio transmission and a planetary gear set.
Tokkai Hei 10-325459 published by the Japanese Patent Office in 1997 discloses an infinite speed ratio transmission combining a toroidal continuously variable transmission (toroidal CVT), fixed speed ratio transmission and planetary gear set.
The infinite speed ratio transmission comprises a first shaft and a second shaft parallel thereto. The first shaft is joined to the engine, and the toroidal CVT is arranged around the first shaft as center. The rotation of the first shaft is output separately through a fixed speed ratio transmission and the toroidal CVT.
A first gear which rotates according to the rotation output of the fixed speed ratio transmission and a second gear which rotates according to the rotation output of the toroidal CVT are provided on the second shaft. A power recirculation clutch, planetary gear set, direct clutch and final output gear are further arranged on the second shaft. The first gear is joined to a planet carrier of the planetary gear set via the power recirculation clutch. The second gear is fixed to a sun gear of the planetary gear set. It is also joined to the second shaft via the direct clutch. A ring gear of the planetary gear set is fixed to the second shaft. The power recirculation clutch and direct clutch are selectively engaged.
In a power recirculation mode where the power recirculation clutch is engaged while the direct clutch is disengaged, the planetary gear set varies the rotation direction and speed of the final output gear according to the difference in the rotation speed of the first gear and the second gear. The reason why the transmission is referred to as an infinite speed ratio is because the output rotation can be held at zero, i.e., the rotation of the final output gear can be stopped, while the rotation input continues.
In this infinite speed ratio transmission, the second gear is provided between the first gear and the final output gear. In other words, the gears are arranged in the order of the first gear, the second gear, and the final output gear on the second shaft.
Here, the axial position of the first gear and the second gear is determined depending on the positioning of the fixed speed ratio transmission and the toroidal CVT, and the distance between the gears cannot be set arbitrarily. In this infinite speed ratio transmission, as the final output gear is situated outside the inter-gear distance, the axial length of the second shaft required for positioning the gears is long.
In this infinite speed ratio transmission, the planetary gear set and power recirculation clutch are disposed between the first gear and second gear, and the direct clutch is disposed between the second gear and the final output gear. Here, a sun gear of the planetary gear set is joined to the second gear, and the planet carrier is joined to the first gear. A ring gear and the final output gear are fixed on the second shaft. As a result of this arrangement, the join parts of the planet carrier and first gear overlap outside the join parts of the ring gear and second shaft, so the dimensions of the planetary gear set increase in the radial direction.
Due to this reason, both the length and outer diameter of this prior art infinite speed ratio transmission is large.
It is therefore an object of this invention to reduce the dimensions of an infinite speed ratio transmission.
In order to achieve the above object, this invention provides an infinite speed ratio transmission comprising a first shaft connected to an engine, a second shaft disposed in parallel with the first shaft, a fixed speed ratio transmission comprising a first rotating element supported free to rotate on the second shaft, a continuously variable transmission comprising a second rotating element fixed to the second shaft, a planetary gear set disposed between the first rotating element and the second rotating element on the second shaft, a final output member, a first clutch and a second clutch.
The first rotating element is arranged to output a rotation of the first shaft at a fixed speed ratio and the second rotating element is arranged to output the rotation of the first shaft at an arbitrary speed ratio.
The planetary gear set comprises a sun gear joined to the second rotating element, a planet carrier joined to the first rotating element, and a ring gear which varies rotation direction and rotation speed according to a difference of a rotation speed of the sun gear and a rotation speed of the planet carrier.
The final output member is joined to the ring gear and is disposed between the planetary gear set and the second rotating element,
The first clutch has a function to disengage a join of the first rotating element and the planet carrier, and the second clutch has a function to join the first rotating element and the final output member.
The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.